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NVD / CVE Program· CNA Linux

CVE-2026-68398: ppp: defer channel free to an RCU grace period to fix pppol2tp RX UAF

Noroxi assessment

Priority: Monitor (action score 31/100)

  • Public proof-of-concept code exists (GitHub); there is no record of exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.23% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 06213c85d8c0994f786c093b8b2a517987943ca6, 110b765744b147c63882f5e9cb12931c5dc8d85f, 3.17; azl3 kernel 6.6.143.1-1 on Azure Linux 3.0 6.6.150.1-1.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 06213c85d8c0994f786c093b8b2a517987943ca6, 110b765744b147c63882f5e9cb12931c5dc8d85f, 3.17; azl3 kernel 6.6.143.1-1 on Azure Linux 3.0 6.6.150.1-1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In the Linux kernel, the following vulnerability has been resolved: ppp: defer channel free to an RCU grace period to fix pppol2tp RX UAF pppol2tp_recv() runs in the L2TP UDP-encap softirq RX path: l2tp_udp_encap_recv() -> l2tp_recv_common() -> pppol2tp_recv() -> ppp_input(&po->chan) It runs under rcu_read_lock() holding only an l2tp_session reference and takes NO reference on the internal PPP channel (struct channel, chan->ppp) that ppp_input() dereferences. The pppox socket is SOCK_RCU_FREE, so 'po' and the embedded ppp_channel are RCU-safe. But the internal struct channel is a separate allocation that ppp_release_channel() frees with a plain kfree(): close(data socket) -> pppol2tp_release() -> pppox_unbind_sock() -> ppp_unregister_channel() -> ppp_release_channel() -> kfree(pch) For a channel that is bound (PPPIOCGCHAN) but not attached to a ppp unit (no PPPIOCCONNECT, pch->ppp == NULL) and not bridged, teardown skips both ppp_disconnect_channel()'s synchronize_net() and ppp_unbridge_channels()'s synchronize_rcu(), so the kfree() has no grace period. rcu_read_lock() in pppol2tp_recv() does not protect against a plain kfree(), so an in-flight ppp_input() on one CPU can dereference the channel just freed by close() on another CPU. The bug is reachable by an unprivileged user. Defer the channel free to an RCU callback via call_rcu() so the grace period fences any in-flight ppp_input(). The disconnect and unbridge teardown paths already fence with synchronize_net()/synchronize_rcu(); call_rcu() does the same here without stalling the close() path.

HighCVSS 7.8 · v3.1—Proof of concept Fix available
Published
Aug 10, 2026
Updated
Oct 19, 2026
EPSS
0.2% · 14th percentile

Report tools

JSON

Action score

31

Monitor

Low priority for now.

CVSS
31 / 40 · 7.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · Linux
7.8
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • Proof of concept exists, no weaponized module
  • A fix has been released

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Follow CVE-2026-68398

When you'll hear from us

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  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • d36e5ba7bbed5d7bd26e8609ffed503c2def401b, 9bcc0508576b2d50efd958f2ea1c5906749c2c89, c2984681fe15cfb803a9132aaaf1140ab20a72c1, 5803ecd7f6ac6f747582e775caa62ac9d0489261, 26f8819ddd10141ebe7bbce700fbab36bfa5f478, 4.15affected
    • ee40fb2e1eb5bc0ddd3f2f83c6e39a454ef5a741 and later · before 4e47f1ac188ece11d6fdabe44166a2776cc5bd4eaffected · git
    • ee40fb2e1eb5bc0ddd3f2f83c6e39a454ef5a741 and later · before 110b765744b147c63882f5e9cb12931c5dc8d85faffected · git
    • ee40fb2e1eb5bc0ddd3f2f83c6e39a454ef5a741 and later · before 4bb84e964ff0fe0a171c965362de72f9820dbce9affected · git
    • ee40fb2e1eb5bc0ddd3f2f83c6e39a454ef5a741 and later · before 3ab32218d7182705dae5c86f13925f458072da2caffected · git
    • ee40fb2e1eb5bc0ddd3f2f83c6e39a454ef5a741 and later · before c9574b8a8edeb4edd3ac6472c27ef7184bdb2baaaffected · git
    • ee40fb2e1eb5bc0ddd3f2f83c6e39a454ef5a741 and later · before 06213c85d8c0994f786c093b8b2a517987943ca6affected · git
    • ee40fb2e1eb5bc0ddd3f2f83c6e39a454ef5a741 and later · before ec4215683e47424c9c4762fd3c60f552a3119142affected · git
    • 3.2.99 and later · before 3.3affected · semver
    • 3.16.54 and later · before 3.17affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.187-16.1.187-1
Debian:12linux-6.12before 6.12.101-1~deb12u16.12.101-1~deb12u1
Debian:13linuxbefore 6.12.101-16.12.101-1
Debian:14linuxbefore 7.1.6-17.1.6-1
Rocky Linux:10kernelbefore 0:6.12.0-211.72.1.el10_20:6.12.0-211.72.1.el10_2

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
    40Plan
  • CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
    40Plan
  • CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-68396Aug 10, 2026 · scsi: core: wake eh reliably when using scsi_schedule_eh
    0Monitor
  • ← EarlierCVE-2026-68397Aug 10, 2026 · net/iucv: take a reference on the socket found in afiucv_hs_rcv()
    35Monitor
  • Later →CVE-2026-68399Aug 10, 2026 · bpf: Fix UAF in sock clone early bailouts
    31Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux06213c85d8c0994f786c093b8b2a517987943ca6Vendor (CNA)
Linux Linux110b765744b147c63882f5e9cb12931c5dc8d85fVendor (CNA)
Linux Linux3.17Vendor (CNA)
Linux Linux3.3Vendor (CNA)
Linux Linux3ab32218d7182705dae5c86f13925f458072da2cVendor (CNA)
Linux Linux4.10Vendor (CNA)
Linux Linux4.15Vendor (CNA)
Linux Linux4.5Vendor (CNA)
Linux Linux4bb84e964ff0fe0a171c965362de72f9820dbce9Vendor (CNA)
Linux Linux4e47f1ac188ece11d6fdabe44166a2776cc5bd4eVendor (CNA)
Linux Linuxc9574b8a8edeb4edd3ac6472c27ef7184bdb2baaVendor (CNA)
Linux Linuxec4215683e47424c9c4762fd3c60f552a3119142Vendor (CNA)
azl3 kernel 6.6.143.1-1 on Azure Linux 3.06.6.150.1-1 · CBL-Mariner ReleasesMicrosoft (MSRC)
debian:linux6.1.187-1 · Debian:12Package registry (OSV)
debian:linux-6.126.12.101-1~deb12u1 · Debian:12Package registry (OSV)
rocky linux:kernel0:6.12.0-211.72.1.el10_2 · Rocky Linux:10Package registry (OSV)

Exploit status

Proof of concept available

A public proof of concept or detection signature exists. Exploit knowledge is out there; don't delay patching.

Evidence

  • Proof-of-concept repository on GitHub ×1

Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.

Public exploit evidence
SourceKindDate
Proof-of-concept repository on GitHubstars:102026-08-12

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Published
  2. First PoC+1 d
  3. TodayNov 7, 2026+89 d
EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-681170 days aparttipc: clear sock->sk on the failed-insert path in tipc_sk_create()
    39Monitor
  • CVE-2026-681270 days apartila: reload IPv6 header after pskb_may_pull in checksum adjust
    39Monitor
  • CVE-2026-681440 days apartphonet: pep: fix use-after-free in pep_get_sb()
    39Monitor
  • CVE-2026-681560 days apartlibceph: refresh auth->authorizer_buf{,_len} after authorizer update
    39Monitor
  • CVE-2026-683810 days apartksmbd: pin conn during async oplock break notification
    39Monitor
  • CVE-2026-684260 days apartxfrm: fix stale skb->prev after async crypto steals a GSO segment
    39Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-416 · Use After Free

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

nvd-secondary

Root cause

After a memory region is freed, another reference pointing to it is still used. By then, the same region may have been allocated for different data.

The bug in code

The whole CWE-416 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

c
free(dev->buf);/* ... another thread is still running ... */process(dev->buf);

Fixed

c
lock(&dev->lock);free(dev->buf);dev->buf = NULL;unlock(&dev->lock);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. SSVC exploitation— → none
  2. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (6 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records